A Study On Preparation Of MgAl₂O₄ Powders With Mg-Al Double Metal Alkoxides By Sol-Gel Technique

The high purity and ultrafine magnesium aluminate powders is mainly used in some high and new technology industries field such as artificial crystal, transparent ceramics, sound intermediate material and so on. Since some traditional methods to prepare the powders are adopted, there are many performance index can't meet the need. Therefore the powders' applications are limited. So the purity and granularity of the powders have become the most important to us.This thesis used ethanol, isopropanol, normal butyl alcohol and isobutanol and uses four methods to prepare double metal alkoxides with iodine used as catalyst. A kind of high purity double metal alkoxides will be attained by using the method of vacuum distillation. Through controlling all kind of factors which affect the performance of the powders, such as the amount of water, the concentration of the double metal alkoxides, the hydrolyzed temperature, the speed of water and pH value, some single factor experiments have been done. Then let the production dry, which apply four methods including nature drying, oven drying, azeotropic distillation drying, and vacuum distillation drying. After drying, the production is calcined with different temperature and the magnesium aluminate powders are prepared.The results show that normal butyl alcohol is suitable for preparation of double metal alkoxides and molar ratio of Mg:Al =1:2. The high purity powders can be prepared by using double metal alkoxides which adopted normal butyl alcohol or isobutanol as reactant with vacuum distillation. The performances of the powders have been investigated with TG-DTA, GSL, XRD, SEM, etc. The results show that the amount of water [the double metal alkoxides/the water (molar ration)] =1:10; concentration of the double metal alkoxides: is between 0.20mol/L and 0.30mol/L; hydrolyzing temperature is 25 C; the speed of adding water is 8-10ml/min; PH value of the solution system should be controlled about 5; the optimum method of drying is vacuum distillation drying; in the interest of the perfect spinel phase, the calcining temperature should be at 1250C.The results above are significant to research and exploit the high purity and ultrafine magnesium aluminate powders.